1. Field
The present invention relates to a rotational atherectomy device for removing or reducing stenotic lesions in blood vessels such as a human artery by rotating an abrasive element within the vessel to partially or completely ablate the unwanted material.
2. Description of Related Art
Atherosclerosis, the clogging of arteries, is a leading cause of coronary heart disease. Blood flow through the peripheral arteries (e.g., carotid, femoral, renal etc.), is similarly affected by the development of atherosclerotic blockages. A conventional method of removing or reducing blockages in blood vessels is known as rotational atherectomy. Such a method and a device for performing the method are described in, for example, U.S. Pat. No. 4,990,134 to Auth. According to Auth, a long guidewire is advanced into the diseased blood vessel across the stenotic lesion. A hollow drive shaft formed from a singe layer of torque transmitting coiled wire(s) is the advanced over the guidewire. The distal end of the drive shaft terminates in a burr provided with an abrasive surface formed from diamond grit or diamond particles. The burr is positioned against the occlusion and the drive shaft rotated at extremely high speeds (e.g., 20,000-160,000 rpm). As the burr rotates, the physician slowly advances it so that the abrasive surface of the burr scrapes against the occluding tissue and disintegrates it, reducing the occlusion and improving the blood flow through the vessel.
It is also known from U.S. Pat. No. 6,132,444 to Shturman (the instant inventor) et al., to provide a drive shaft with an eccentric enlarged diameter segment positioned proximally to and spaced away from the distal end of the drive shaft. According to U.S. Pat. No. 6,132,444 to Shturman, abrasive particles are located around a maximum diameter of said eccentric enlarged diameter segment of the drive shaft thereby forming an eccentric abrasive element positioned proximally to and spaced away from the distal end of the drive shaft. According to U.S. Pat. No. 6,132,444 to Shturman, the drive shaft is formed from a single layer of torque transmitting coiled wire(s).
The prior art rotational atherectomy devices such as those referred to above comprise an elongated drive shaft rotatable around a stationary guidewire. A long proximal portion of the drive shaft is rotatable within an elongated stationary drive shaft sheath, said drive shaft sheath forming an annular lumen between the stationary sheath and the rotatable drive shaft. A saline solution or special lubricating fluid is pumped into the annular lumen between the stationary sheath and the rotatable drive shaft. A portion of said saline solution or special lubricating fluid is able to pass between adjacent wire turns of the drive shaft into a second annular lumen formed between the drive shaft and the guidewire thereby reducing friction between the drive shaft and the guidewire. In all of the prior art rotational atherectomy devices referred to above the antegrade flowing saline solution or special lubricating fluid enters the treated vessel from distal end of the stationary drive shaft sheath and thereby entrains and propels distally in an antegrade direction along the treated vessel abraded particles (debris) removed by the abrasive element. The distal migration of the abraded particles (debris) in an antegrade direction and embolisation of very small diameter arteries or capillaries by said abraded particles is of major concern to physicians who practice in this field. Clearly, the existence of particulate matter in the blood stream is undesirable and can cause potentially life-threatening complications, especially if the particles are over a certain size.
Although the potentially detrimental effect caused by the presence of abraded particles in the blood vessels is reduced if they are very small microparticles, it is much more preferable to remove from the treated blood vessel any debris abraded or otherwise released from the stenotic lesion during treatment and thereby prevent migration of debris to other locations along the treated blood vessel.
A rotational atherectomy device, described in U.S. Pat. No. 5,681,336 (to Clement et al.), has been proposed. This device attempts to prevent migration of abraded particles distally along the treated blood vessel by removing the ablated material from the blood vessel whilst the device is in use. The rotational atherectomy device known from U.S. Pat. No. 5,681,336 (to Clement et al.) has a complicated construction and is difficult to manufacture on a commercial scale.
A number of disadvantages associated with the known rotational atherectomy devices have been addressed in WO 2006/126076 to Shturman (the instant inventor). All of the embodiments described in WO 2006/126076 comprise a rotatable fluid impermeable drive shaft and allow delivery of pressurized fluid from a lumen of the rotatable fluid impermeable drive shaft into the treated vessel distal to the abrasive element so that at least a portion of said fluid flows in a retrograde direction along the treated vessel between the stenotic lesion and the vessel wall and entrains the abraded particles removed by the abrasive element. The retrograde flowing fluid and entrained abraded particles are aspirated from the treated vessel and out of the patient's body.
All embodiments shown in WO 2006/126076 illustrate a torque transmitting element of the fluid impermeable drive shaft being formed by a single multifilament metal torque transmitting coil which extends distally through and distal to the abrasive element. An atherectomy device having this design allows excellent transmission of torque to the abrasive element by the torque transmitting coil, but does not enable the device to have a sufficiently small transverse cross-sectional dimension to cross very tight stenotic lesions.